Various manufacturing methods have heretofore been known with respect to a ceramic honeycomb structure in which cells in opposite end faces of a ceramic honeycomb body having a plurality of cells and formed into a honeycomb shape are alternately sealed. For example, a method of manufacturing a ceramic honeycomb structure has been proposed in which a slurry for sealing is filled into opening parts of the cells in the end faces of the ceramic honeycomb body using masks having holes drilled in positions corresponding to the opening parts of the cells and in which the body is fired and formed. Concretely, as shown in FIG. 8(a), rubber or soft resin masks 24, 25 are prepared in which holes 23 are made in positions corresponding to opening parts of cells 22 to be sealed in the end faces of a ceramic honeycomb body 21, and the masks 24, 25 are disposed on the respective end faces of the ceramic honeycomb body 21 by a manual operation. In this case, to form the ceramic honeycomb structure into a configuration in which the cells 22 are alternately sealed in the opposite end faces of the ceramic honeycomb body 21, that is, only the opening part of each cell 22 in one end face is sealed, the masks 24, 25 are formed in such a manner that the drilled holes 23 are arranged in exactly opposite patterns.
Next, as shown in FIG. 8(b), one end face of the ceramic honeycomb body 21 on which the mask 24 is disposed is immersed into a sealing slurry 26, and pressure is applied to the other end face thereof. Accordingly, the sealing slurry 26 is forced/charged into the opening parts of the cells 22 (see FIG. 8(a)) via the holes 23 (see FIG. 8(a)). The mask 25 (see FIG. 8(a)) is similarly disposed on the other end face of the ceramic honeycomb body 21, and the sealing slurry 26 is charged into the opening parts of the cells 22 (see FIG. 8(a)). In the above-described steps, as shown in FIG. 8(c), after charging the sealing slurry 26 into the opening parts of the cells 22 to be sealed in the opposite end faces of the ceramic honeycomb body 21, the body is fired, and accordingly a targeted ceramic honeycomb structure can be manufactured.
However, in the above-described method of manufacturing the ceramic honeycomb structure, as shown in FIG. 8(a), there have been inconveniences that the masks 24, 25 having the holes 23 in the positions corresponding to the opening parts of the cells 22 are prepared and that it is difficult to correctly dispose the masks 24, 25 on the respective end faces of the ceramic honeycomb body 21. Especially, in a large-sized structure having a diameter of about 300 mm, for which there has been a rising demand in recent years, or in a ceramic honeycomb structure having a high cell density, the number of the opening parts of the cells 22 in the end face reaches several tens of thousands, and this further makes it difficult to dispose the above-described masks 24, 25. Since the masks 24, 25 are disposed on the respective end faces of the ceramic honeycomb body 21 by the manual operation, there have been inconveniences that operator's skill is required, much time is taken, and it is impossible to cope with automation. Furthermore, to reuse the masks 24, 25, the masks need to be cleaned after end of the operation, but the enormous number of the holes are made in the masks 24, 25 as described above, and therefore there has also been an inconvenience that the cleaning is troublesome and time-consuming.
In consideration of these circumstances, in Japanese Patent Application Laid-Open No. 2001-300922, a manufacturing method has been described in which sheets are attached to the opposite end faces of the ceramic honeycomb body formed into a honeycomb shape having a plurality of cells, holes are drilled in the sheets at positions corresponding to the opening parts of the cells, and the slurry for sealing is charged into the opening parts of the cells in the opposite end faces of the ceramic honeycomb body via the holes. Thereafter, the body is fired to manufacture the ceramic honeycomb structure in which the opening parts of the cells are alternately sealed.
In the ceramic honeycomb structure constituted in this manner, disposable sheets which are to be attached to the end faces of the ceramic honeycomb body and in which the holes are drilled are used instead of the masks. Therefore, as compared with the method of manufacturing the ceramic honeycomb structure by the use of the masks, it is easy to dispose the sheets which are substitutes for the masks on the ceramic honeycomb body, and it is also easy to cope with the automation of manufacturing steps.
However, in the above-described method of manufacturing the ceramic honeycomb structure, there has been a problem that it is remarkably difficult to position the holes to be drilled in the sheets with respect to the opening parts in several tens of thousands of cells of the ceramic honeycomb structure in manufacturing the large-sized ceramic honeycomb structure. In a case where the holes are not correctly positioned, there has also been a problem that the holes are drilled in the same cell in the opposite end faces, and an object to alternately seal the cells cannot be achieved. When the ceramic honeycomb body is even slightly curved/deformed, the above-described problem is further complicated.
The present invention has been developed in consideration of the above-described problems, and an object thereof is to provide a method of manufacturing a ceramic honeycomb structure, and a ceramic honeycomb structure in which a reference cell different in a shape of an opening part in an end face from other cells is used as a reference point in drilling holes in sheets attached to the end faces of a ceramic honeycomb body having a plurality of cells. Accordingly, the positioning of the holes is facilitated, further in a drilling step of the ceramic honeycomb body, the holes can be quickly positioned, and the obtained ceramic honeycomb structure can be constituted inexpensively.